CHICAGO – The Red Sox’ hitting coaches feel Jacoby Ellsbury is about to break out. They see the progress in the leadoff hitter’s swing in batting practice and feel it’s just a matter of time.

“He hasn’t yet taken what he does in batting practice to the game,’’ said assistant hitting coach Victor Rodriguez. “It’s about him being more aggressive earlier in the count. He’s getting there. The power is there. The strength is there. I think it’s only a matter of time before we see the Ellsbury we know and love.’’

Which is why the Red Sox should not let him go off into free agency without fighting to keep him. There seems to be a feeling out there that the Red Sox will simply let Ellsbury go at season’s end, similar to the way they let closer Jonathan Papelbon walk after the 2011 season.

That thinking did not work in the Papelbon situation. The Red Sox have not been able to adequately replace him. And it says here they won’t be able to replace Ellsbury, either.

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When Ellsbury is clicking, there’s no better player in the organization. You can speak of Jackie Bradley Jr.’s upside and about him being Ellsbury’s heir apparent. But until he does what Ellsbury’s done in the majors, you can’t say he’ll be a better player.

We have taken our shots at Ellsbury over the years, accusing him of milking injuries and being soft. It’s not that I take any of that back, but I’ve grown to realize what Ellsbury is. He’s not a bad guy. He’s just a quiet guy, who simply doesn’t like the limelight.

If he could play with the curtain drawn and still make $9 million, he would. He doesn’t like media attention of any kind. He’d rather drive off the road than speak to the media. He doesn’t do it to be nasty, because that’s not in his nature. He seems like a nice person who just likes to keep to himself, and for that, we’re not going to criticize him.

In almost 30 years of being around Red Sox teams, I can’t remember a player with six years of service who I know so little about.

Having said that, the Red Sox should think long and hard about retaining him.

They think they might have a replacement in Bradley Jr. and/or Shane Victorino, who has won two Gold Gloves in center field. But Ellsbury’s skill set is off the charts.

Over the past year, Ellsbury has been a pretty ordinary player. Even with his struggles this season, he is among the major league leaders in steals (13) and triples (4). He began this season hitting .290 with a .340 on-base percentage over his first 30 games, but is hitting just .143 with a .239 OBP over the last 15 games. And so far he has remained healthy — second in the majors with 194 at-bats.

Red Sox manager John Farrell has repeatedly said he isn’t running away from Ellsbury, though if Victorino were healthy you might see Ellsbury drop in the order. Farrell wishes he wouldn’t carry one at-bat into another, but that’s what Ellsbury seems to do. In some ways it shows he does care how his performance affects the team.

There’s a school of thought that the team would seek to deal Ellsbury at the trade deadline. Seriously? You’re going to trade your best athlete at the deadline if you’re in contention? If the Red Sox fell hopelessly out of it, you could see it, but the Red Sox seem more than willing to carry this out until the end, see how Ellsbury performs before making a decision.

They would likely make him a qualifying offer and reap the benefits of a first-round draft pick should another team sign him. And you know there will be a market. The Rangers, Mets, Yankees, Mariners, Cubs, and others would be interested.

None of us really know what has caused Ellsbury’s recent decline.

There could be pressure to perform in his free agent year. Maybe that pressure is getting to him. On the other hand, he seems pretty unaffected by his environment and has told friends he would like to remain in Boston long term.

In that respect he is a creature of habit, much like Carl Crawford was in Tampa Bay.

Crawford felt comfortable in Tampa Bay, but once he got to the spotlight of Boston after signing for $20-plus million a year, it was different for him. That’s why Ellsbury wouldn’t necessarily want to go anywhere else. As magnifying as Boston is, Ellsbury has found a way to hide.

And that’s what agent Scott Boras will have to weigh when Ellsbury hits free agency.

Depending how this season goes, Ellsbury could be one of the most sought-after players in free agency, or he might be similar to Michael Bourn, another Boras client, who had to wait until the bitter end before Cleveland signed him to a four-year, $40 million contract.

Based on his numbers two years ago and based on what he’s done in other years, it’s so hard to figure out who Ellsbury is. Since hitting .321 with 32 homers and 105 RBIs with a .928 OPS and 39 steals in 2011, he’s hit .259 in his last 497 at-bats with five homers and 40 RBIs.

Is it just coming back from injuries and not quite being able to get back in the groove? Is it changing his approach at the plate?

“We’ve watched his video from two years ago and there’s nothing different,” Rodriguez said. “He’s probably lost some aggressiveness and confidence, but he’s got all the skills.”

You won’t find more than a dozen players who have better skills than Ellsbury.

Once he finds consistency (he went 2 for 3 with two walks in Wednesday night’s 6-2 win over the White Sox), Ellsbury is capable of eye-opening, jaw-dropping things. And there aren’t many players through the Red Sox organization or in major league baseball you can say that about.

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